In recent years, soft silicone hydrogel contact lenses become more and more popular because of their high oxygen permeability and comfort. One of lens forming materials widely used in making silicone hydrogel contact lenses is polymerizable polysiloxane. The main function of the polymerizable polysiloxane is to provide high oxygen permeability to resultant contact lenses.
However, it is known that polysiloxanes has a great tendency to migrate onto the surface of a substrate made of material containing polysiloxanes to minimize the surface energy of the substrate. Contact lenses with a high amount of polymerizable polysiloxane(s) generally exhibit poor wettability and generally require a surface treatment.
In addition, because of its hydrophobic nature, a polymerizable polysiloxane is generally not compatible with hydrophilic components in a lens formulation, including, e.g., hydroxyethylmethacrylate, hydroxyethylacrylate, N,N-dimethylacrylamide, N-vinylpyrrolidone, or an internal wetting agent. It would be difficult to obtain homogeneous lens formulations.
Therefore, there is still a need for polymerizable polysiloxane which are relatively more compatible with the hydrophilic components of a lens formulation for making silicone hydrogel contact lenses and can improve the surface wettability of contact lenses made from such lens formulation.